An IC package includes a high thermal conductivity insulating material substrate, such as polycrystalline diamond, on which the IC is mounted for thermal management. The electrical lead pins of the package are electrically connected to the IC and thermally connected to the substrate.
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17. An integrated circuit package comprising:
a) an integrated circuit, b) a lead frame having a plurality of electrically conductive legs in electrical connection with the integrated circuit and extending outside of the package, and c) a diamond film base, wherein the diamond film base is in intimate thermal contact with both the integrated circuit and the plurality of legs of the lead frame.
1. A plastic encapsulated integrated circuit package comprising:
a) a thermally conductive, electrically insulating base, b) an integrated circuit mounted on the base, and c) a plurality of electrically conductive legs in electrical connection with the integrated circuit and extending outside the package, wherein the base is in intimate contact with both the integrated circuit and the plurality of legs.
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The ever-increasing demand for smaller, higher performance information systems has lead to the adoption of the integrated circuit ("IC") as the information processing center of the modern computer. These integrated circuits, or chips, are typically housed within standard ceramic, plastic or metal packages and carry information between the chip and other information processing units within the system.
In one type of plastic encapsulated dual in-line package, such as the package 1 shown in
Because electrical inefficiencies in the chip generate heat, the temperature of both the chip 2 and other parts of the package supporting the chip 2 significantly rise during use. It is known that such elevated temperatures can degrade the IC's performance. For example, because many of the IC's critical processes rely on electron kinetic phenomena which become accelerated by increased temperature, failures in metallization and bonded interfaces occur during extended use. Accordingly, heat production by the chip, often termed "thermal density", has become a significant design consideration which threatens to limit the further miniaturization of information systems within reasonable cost constraints.
Conventional treatment of the thermal density problem has met with limited success. For example, in the prior art design shown in
Therefore, it is the object of the present invention to provide a package which can provide electrical connection between the chip and the lead frame, yet still maintain the chip at low temperatures.
In accordance with the present invention, there is provided a plastic encapsulated integrated circuit package comprising:
a) a thermally conductive, electrically insulating resistive base,
b) an integrated circuit mounted on the base,
c) a plurality of legs in electrical connection with the integrated circuit, and wherein the base is in intimate thermal contact with both the integrated circuit and the plurality of legs of the lead frame.
Also in accordance with the present invention, there is provided an integrated circuit package comprising:
a) an integrated circuit,
b) a lead frame having a plurality of legs in electrical connection with the integrated circuit, and
c) a diamond film base, wherein the diamond film base is in intimate thermal contact with both the integrated circuit and the plurality of legs of the lead frame.
It has been found that mounting a conventional chip on a thermally conductive, electrically insulating resistive substrate (such as diamond film) and providing intimate thermal contact of it with leads allows each of the leads to be used as a direct conduit for thermal dissipation. Because these leads have thicknesses of about 0.010 inches, they possess a much greater cross-section than the conventional wires, and are therefore more thermally conductive than the plastic encapsulent, the present invention provides for increased heat dissipation from the entire package yet does not interfere with its electrical properties.
For the purposes of the present invention, "intimate thermal contact" means that the thermal conductivity of the interface connecting the IC die pad to the lead exceeds 2 W/cm K, so that there is essentially no thermal resistance provided by any gap therebetween. Preferably, the base touches both the leads and the chip.
Any substrate having a thermal conductivity of at least about 2 W/cm K and an electrical resisitivity of at least about 106 ohm-cm at 10 V dc can be used as the thermally conductive, electrically resisitive base of the present invention. These substrates include, but are not limited to, diamond, aluminum nitride, beryllia, diamond-coated substrates, and insulator-clad metals. Preferably, the thermal conductivity of the base is at least about 6 W/cm K, more preferably at least about 10 W/cm K. Preferably, the electrical resisitivity of the base is at least about 108 ohm-cm, more preferably exceeds 1010 ohm-cm. The thickness of the base may be between about 100 and about 500 um, preferably between about 150 and 200 um.
Most preferably, the base is diamond film because it is both an excellent thermal conductor and an excellent electrical insulator. Such diamond film can be any high thermal conductivity diamond (free standing or coating). In some embodiments, the base is a diamond film having a thermal conductivity of at least about 10 W/cm K and an electrical resisitivity of at least about 1010 ohm-cm. Typically, the diamond film is chemically vapor deposited (CVD) diamond which has a thickness of between about 150 and about 200 microns. Because the diamond film can be so thin, its utilization in the present invention offers a design advantage in that it can be incorporated into conventional system designs without a significant change in the package geometry.
In one embodiment of the present invention, as shown in
In one embodiment of the present invention containing 24 legs, finite element analysis revealed that the Tja (i.e., the temperature differential between the device junction and the ambient temperature) was only about 60 degrees C. In contrast, the Tja for a comparable conventional IC package was about 400 C. for the same power input.
The method by which the diamond film is attached to the chip can be any conventional attachment means, including soldering, clamping, bonding agents, and silver loaded epoxies. Similarly, the method by which the diamond film is attached to the legs of the package can be any conventional attachment means, including clamping, soldering, bonding agents, silver loaded epoxies, and brazing.
Any conventional chip and lead frame design can be used with the present invention as long as the design allows for a diamond film to be in intimate thermal contact with both the chip and the legs of the lead frame. Conventional chips include integrated circuits and discrete active devices such as transistors and diodes. Conventional package designs include both plastic and ceramic DIP, SIP, PGA, QFP, BGA and LCC designs. When a thermally conductive, electrically resistive substrate other than diamond is also used for a die pad, the IC package of the present invention is plastic encapsulated.
Because the thermally conductive, electrically resistive base of the present invention provides for greater heat dissipation, the IC packages of the present invention can tolerate larger amounts of power than the standard package without exceeding the critical device junction temperature. In particular, the present invention provides an improved JEDEC package capable of dissipating up to at least about 600% more power than the standard JEDEC package in forced air with a convection coefficient of about 50 W/m2 C. at 50 C. while still maintaining a maximum junction temperature of 125 C. In one embodiment, finite element analysis revealed that a 24 pin DIP of the present invention was capable of dissipating about 12 watts of power in forced air with a convection coefficient of about 50 W/m2 C. at 50 C. while still maintaining a maximum junction temperature of 125 C. In contrast, the standard JEDEC 24 pin DIP could dissipate only 1.6 watts.
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Jul 01 1994 | Saint Gobain/Norton Industrial Ceramics Corporation | (assignment on the face of the patent) | / | |||
Jul 01 1994 | NAGY, BELA | Saint-Gobain Norton Industrial Ceramics Corporation | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 007071 | /0634 | |
Jul 01 1994 | PARTHA, ARJUN | Saint-Gobain Norton Industrial Ceramics Corporation | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 007071 | /0634 |
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